In the related art, a display system has been widely known which superimposes a guide line indicative of a traveling direction of a vehicle on an image of a vehicle rear and displays the same on a display when moving backward a vehicle such as an automobile and parking the vehicle in a parking space (for example, refer to Patent Document 1). The display system is generally configured to share the display with a navigation system and an audio system and to switch an image to be displayed on the display in correspondence to a shift position of the vehicle. For example, when a driver changes the shift position to a reverse position, the display system displays the rear image on the display. Also, when the driver changes the shift position to a position other than the reverse position, the display system displays an image of the navigation system, the audio system or the like on the display.
The display system includes, for example, a rear camera configured to capture the rear of the vehicle, a microcomputer (hereinafter, also referred to as ‘main microcomputer’) configured to select an image to be displayed on a display device in correspondence to the shift position, a microcomputer (hereinafter, also referred to as ‘sub-microcomputer’) configured to depict a guide line, and a display controller configured to enable the main microcomputer to display the selected image on the display device. The main microcomputer is configured to acquire a vehicle signal indicative of the shift position of the vehicle. When it is detected that the shift position becomes the reverse position, the main microcomputer selects the rear image captured by the rear camera, instead of an image upon forward movement, and instructs the sub-microcomputer to depict the guide line. The display controller enables the main microcomputer to superimpose the guide line depicted by the sub-microcomputer on the selected rear image and to display the same on the display device.
Patent Document 1: JP-A-2012-216997
Patent Document 2: JP-A-2009-284023
Patent Document 3: JP-A-2014-88128
In the case of the display system as described above, a time lag occurs after it is detected that the shift position becomes the reverse position and the main microcomputer selects the rear image until the sub-microcomputer generates the guide line. Therefore, when the shift position is changed during the time lag, an appropriate image may not be output. For example, when the shift position becomes a position other than the reverse position, the main microcomputer cancels the display of the rear image and the sub-microcomputer outputs the guide line depicted in accordance with the instruction before the change. If such a situation occurs, the guide line is superimposed on an image other than the rear image, so that an abnormal image is displayed.